The Ryans had a total adjusted gross income of $323,416 in 2011, up from $215,417.

Tax returns have become a big issue in this presidential campaign, because Romney has refused to release more than the legally-required two years.

Democrats have called for up to 10 years and have pointed out that Romney's father released 12. Romney has said that he will not release any more because Democrats will distort the contents and use it as ammunition in the campaign.